One of a mayor's most critical roles is to set the tone for a city. Which brings us to Oakland Mayor Jean Quan and her oddly passive acceptance of the prospect that just "one person with a bike getting through a fence" could shut down the city's engine of commerce, the Port of Oakland.

Equally puzzling was Quan's assessment of what it would take to keep the port open against a future demonstration: At least 500 officers would need to be deployed - "and if the port wants to pay for that, we can do that," she said. On top of that, the mayor told Chronicle editors in a meeting Wednesday that it was "absolutely" impossible to promise that the port could be kept open in future protests.

What a dispiriting message to send businesses that depend on the port for shipping and receiving of goods.

What they want to hear - what they deserve to hear - is a mayor who will invoke any legal means necessary to keep the port operating. They deserve to hear a mayor who believes that free speech rights end at water's edge when they usurp the rights of hardworking people whose livelihoods depend on goods flowing freely through the port.

Quan should be outraged that a faction of the City Council blocked consideration of a resolution calling on the city to do what was necessary "to prevent future shutdowns or disruptions." Oaklanders should be outraged that a resolution was even necessary; the mayor should be sending that unequivocal message. But she isn't.

At the meeting, Quan expressed frustration at negative stereotypes about Oakland, and bemoaned what she perceived as shrinking local news coverage. But she acknowledged that she may have missed some stories, because she reads the local newspapers' online versions: She subscribes only to the New York Times print edition.

She also veered back and forth between accepting accountability for the Occupy Oakland fiascos and dissociating herself from tactical decisions that proved controversial, such as whether a sufficient number of cops were deployed during the Dec. 12 demonstration.

Oakland's image as a place that's well run and open for business would be helped immensely if the city showed its seriousness about choosing commerce over a handful of protesters who are determined to disrupt it.

To borrow a phrase, it only takes one person to send that message. That person is the mayor.